Abstract: To reveal the compaction characteristics of residual and colluvial soil slopes in the mountainous areas of western China, multi-level static-loading orthogonal tests were conducted to analyze the effects of initial water content, the content of silt and clay particles, and the weight of the overlying soil layer on the compaction characteristics of such soils. The results showed that: ① Under a single-level overlying load, the specimen experienced four deformation stages: rapid, fast, slow, and stable settlement. Under multi-level static loads, the settlement deformation exhibited a continuous stepped pattern. For the first-stage load, both the stage settlement and deformation rate were the largest, followed by a stage-by-stage nonlinear attenuation trend.② The dry density of the specimen increased rapidly at first and then slowly with increasing load, with the increase rate under the first-stage loading reaching as high as 5.1%~8.6%. Water content had a nonlinear promoting effect on the dry density of soil specimens, whereas the content of silt and clay particles showed an attenuating effect.③ Based on compaction theory and experimental observations, a multi-parameter density prediction model for coarse-grained soil was established, which considers the influences of initial water content, the content of silt and clay particles, and the weight of the overlying soil layer. The good applicability of the theoretical model was validated against experimental data. These findings provide a theoretical basis for the scientific prevention of geological disasters in accumulation layers in western China and for quality control in coarse-grained filling engineering.